Curable thermally ejectable printing fluid

ABSTRACT

A curable printing fluid composition for a thermal fluid ejection device is disclosed, wherein the printing fluid composition comprises a curable liquid-phase monomer, a volatile driver fluid capable of being vaporized by a thermal fluid ejection printhead, and a resistor protectant.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of U.S. Provisional PatentApplication Ser. No. 60/664,201 , titled NON-AQUEOUS RADIATION-CURABLEINK COMPOSITION AND METHOD OF PRINTING IN THERMALLY DRIVEN INKJETSYSTEMS and filed Mar. 23, 2005 , the disclosure of which is herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to curable thermally ejectable printingfluids and methods for printing with curable thermally ejectableprinting fluids.

BACKGROUND

Fluid ejection printing devices, such as inkjet printers, print aprinting fluid onto a page by ejecting droplets of the fluid onto aprinting medium. Some fluid ejection printing devices print by producinga continuous stream of printing fluid droplets, for example, with apiezoelectric device, and then selectively deflecting the individualdroplets to print a desired pattern of droplets onto the printingmedium. Other fluid ejection printing devices, known as “drop-on-demand”devices, selectively eject drops of printing fluid, rather thancontinuously. Some devices utilize piezoelectric elements to trigger theejection of printing fluid via a change in ejection chamber volume,while others use electrically resistive elements to thermally vaporize acomponent of the printing fluid, thereby selectively generating a bubbleto drive printing fluid out of each orifice.

Thermal fluid ejection printing devices typically include an array ofprecisely formed nozzles (typically having a diameter betweenapproximately 8 and 60 microns) located on a nozzle plate and attachedto a printhead substrate. The substrate includes an array of firingchambers that receive printing fluids from one or more printing fluidreservoirs. Each chamber has a thin-film resistor, which may be referredto as a “firing resistor”, located opposite the nozzle. Printing fluidcollects between the nozzle and the firing resistor for ejection throughthe nozzle. The substrate and nozzle plate are held and protected by anouter packaging, sometimes called a print cartridge. The total assemblymay be referred to as a printhead. The firing of printing fluid dropletsis typically controlled via a microprocessor. Upon energization of thefiring resistor, a bubble of vaporized printing fluid components formson the resistor, thereby expelling a droplet of printing fluid throughthe nozzle.

Many different types of printing fluids are known, including non-curableand curable printing fluids. Conventional thermally-ejectable printingfluids are generally aqueous-based and are non-curable. Therefore, thefluids tend to be relatively slow drying, and susceptible to smearingand color running during drying. In contrast, curable printing fluidsoffer the advantage of fast, almost instantaneous, drying times, therebyallowing a printed item to be handled almost immediately after printing.Instantaneous curing also enables the use of a much broader range ofsubstrates, such as non-porous substrates, which do not absorb the ink.Examples include, but are not limited to, glass, plastic, metal, andmany plastic coated paper products.

Generally, curable printing fluids include a polymerizable componentthat is cured by exposure to an energy source, such as UV light, heat,an electron beam, etc., after printing. Curable printing fluids also mayhelp to reduce crusting or clogging of the printhead by remaining in theliquid phase inside of the printhead, thereby reducing servicingrequirements.

However, current curable fluid ejection printing fluids may suffervarious drawbacks. For example, conventional curable fluid ejectionprinting fluids may not be printable via thermal ejection, and thereforemay require the use of more expensive and maintenance intensivepiezoelectric printheads. Additionally, some curable printing fluids mayinclude organic solvents such as methyl ethyl ketone in which thecurable components are dissolved. Such solvents may require additionalequipment and care for safe evaporation and disposal.

SUMMARY

One embodiment provides a curable printing fluid composition for athermal fluid ejection device, wherein the printing fluid compositioncomprises a curable liquid-phase monomer, a volatile driver fluidcapable of being vaporized by a thermal fluid ejection printhead, and aresistor protectant.

DETAILED DESCRIPTION

The present disclosure provides various embodiments of curable,thermally ejectable printing fluids suitable for use in thermal fluidejection printing devices. In some embodiments, the printing fluidincludes at least one curable monomer, a volatile driver fluid to drivethe ejection of the printing fluid from a thermal fluid ejectionorifice, and a resistor protectant for improving the lifetime of athermal fluid ejection device used to print with the fluid. Variousembodiments of the printing fluid also may include other components,including but not limited to one or more colorants, oligomers,polymerization initiators, adhesion promoters, etc. Furthermore, aprinting fluid according to the present disclosure may be substantiallynon-aqueous, yet may possess physical characteristics that permit thefluids to be printed with a thermal fluid ejection printing devicedesigned for printing aqueous printing fluids.

One example of a specific application for which a rapidly curableprinting fluid may offer advantages over non-curable printing fluids isin the coding of products during a manufacturing process. Such printingmay occur while the product or product part is moving along a conveyoror assembly line, sometimes at high speeds. Under such conditions,non-curable printing fluids may smear or spread upon contact with otherproduct or downstream structures. This may cause the printed productcode to be difficult to read by downstream scanners and/or workers, andtherefore may result in manufacturing errors. However, a curableprinting fluid may be cured immediately after printing, providing aninstantly durable, high-quality image and thereby minimizing smearing orspreading. Other applications include mail addressing, CD labeling, IDcard printing, web printing, mail printing, outdoor signage printing,and many other applications where printing occurs on non-poroussubstrates and also in applications in which the product is contacted orstacked immediately requiring a marking process that dries immediately.

Prior curable printing fluids for fluid ejection printing devices havegenerally been configured for use in piezoelectric fluid ejectionprinting devices, in both drop-on-demand and continuous-dropconfigurations. However, piezoelectric fluid ejection devices maypresent various drawbacks compared to thermal fluid ejection devices.For example, piezoelectric printheads typically cost more than thermalprintheads. For this reason, piezoelectric printheads generally areprovided as separate components from the printing fluid supply. Incontrast, the relatively low cost of many thermal fluid ejectionprintheads allow them to be integrated into disposable or replaceableprinting fluid supply cartridges. Therefore, thermal fluid ejectionprintheads may have lower initial and repair/replacement costs thanpiezoelectric printheads.

The desired physical properties of a printing fluid may depend on theintended use of the printing fluid. For example, to be ejectable from aconventional thermal printhead designed for an aqueous-based printingfluid, the fluid should have a viscosity in a range of 1-20 cps, asurface tension in a range of 20-50 dyne/cm, and an ability to form adrive bubble to force printing fluid out of the printhead nozzle. Also,the printing fluid should be able to withstand the elevated temperaturesthat may be encountered during thermal fluid ejection without degradingprinting quality and/or printhead performance to an unsatisfactoryextent.

Current curable piezoelectric printing fluid formulations may beunsuitable for use with a thermal fluid ejection printhead. For example,current curable piezoelectric printing fluid formulations may be unableto form a drive bubble of sufficient strength to eject a fluid dropletfrom the nozzle. Additionally, piezoelectric printing typically occurswith a printing fluid temperature at or around room temperature or up to˜50 degrees C. In contrast, temperatures within a thermal fluid ejectionfiring chamber can exceed 300 degrees C. Piezoelectric printing fluidstherefore may not be suitable for operation in this environment.

In contrast, the disclosed printing fluids may be both curable andejectable via a thermal fluid ejection printhead. The rapid curabilityof the disclosed printing fluids may allow the fluids to be used inapplications in which fast drying times are required, including but notlimited to product coding applications. As mentioned above, a printingfluid according to the present disclosure may include one or morecurable monomers that are polymerizable to cure the monomers afterprinting. Besides being curable, a monomer or monomer mixture may beconfigured to have viscosity and surface tension characteristicssuitable for proper fluid ejection from a selected thermal fluidejection printhead. For example, where a thermal fluid ejectionprinthead is configured for the ejection of aqueous-based printingfluids, the monomer or monomer mixture may be configured to have aviscosity in a range of 1-20 cps, and a surface tension in a range of20-50 dyne/cm. It will be appreciated that the surface tension and/orviscosity of the monomer or monomer mixture may be modified asappropriate by other printing fluid components, including but notlimited to the driver fluid, initiators, resistor protectants, etc.Furthermore, it will be appreciated that other viscosity and surfacetension ranges may be appropriate depending upon the specificrequirements of a selected printing device.

The use of a liquid phase monomer or monomer mixture allows the monomeror mixture to be a primary or substantial component of the printingfluid. In this manner, the curing of the monomer on a printing mediumconverts the liquid phase monomer or monomer mixture into a solid phase,thereby greatly reducing or even eliminating the need for drying theprinting fluid after printing compared to conventional aqueous orsolvent-based thermally ejectable printing fluids. The rapid cure timemay help to prevent smearing or running of colors. Furthermore, the lowsolvent content of such a printing fluid compared to prior solvent-basedprinting fluids may help to prevent the outgassing of harmful organicsolvents during drying.

Depending on the application for which a printing fluid is used, aprinting fluid according to the present disclosure may include at leastone mono-functional monomer and at least one multi-functional monomer.The mono-functional monomer may have a lower viscosity than themulti-functional monomer, which may help to lower the overall viscosityof the printing fluid. On the other hand, the multi-functional monomermay permit cross-linking of the printed polymer film to occur, which mayimprove the durability of the printed polymer film compared to a linearpolymer printed film. Mixtures of mono- and di-functional monomers mayprovide better thermal fluid ejection printing performance than mixturesof higher functional monomers. For example, it has been found thatmonomer mixtures containing some higher-functional monomers may resultin the formation of deposits on the firing resistors (“koga”) morerapidly than for mixtures without the higher-functional monomers, whichmay shorten the printhead lifetime. In alternative embodiments, printingfluids may have only monofunctional monomers, or no monofunctionalmonomers.

Any suitable monomer or mixture of monomers may be used. Examples ofsuitable monomers include, but are not limited to, acrylic monomers withfunctionalities of one or more. Some specific examples of suitablecommercially available monomers may include, but are not limited to, thefollowing available from Sartomer of Exton, Pa.: SR-201 allylmethacrylate, SR-203 tetrahydrofurfuryl methacrylate, SR-206 ethyleneglycol demethacrylate, SR-212 1,3 butylene glycol diacrylate, SR-213 1,4butane diol dimethacrylate, SR-238 1,6 hexanediol diacrylate, SR-2562-(2-ethoxyethoxy) ethylacrylate, SR-259 polyethylene glocol (200)diacrylate, SR-295 pentanerytheritol tetraacrylate), SR-306 tripropyleneglycol diacetate), SR-313B lauryl methacrylate, SR-335 lauryl acrylate,SR-339 2-phenoxyethyl acrylate, SR-339A proprietary, SR-344 polyethyleneglocol (400) diacrylate, SR-355 di-trimethylopropane tetraacrylate,SR-368 tris-(2hydroxy ethyl) isocyanurate triacrylate, SR-395 isodecylacrylate, SR-399 dipentanerytheritol pentaacrylate, SR-415 ethoxylated(20) trimethylopropane triacrylate, SR440 isooctyl acrylate, SR-444pentanerythritol triacrylate, SR-489D proprietary, SR-492 propoxylated(3) trimethylopropane triacrylate, SR-493D tridecyl methacrylate, SR-494ethoxylated (4) pentacrytheritol tetraacrylate, SR-506 isobornylacrylate, SR-508IJ dipropylene glycol diacrylate, SR-9003 propoxylatedneopentyl glycol diacrylate, SR-9008 alkoxylated trifunctional acrylateester, SR-9011 trifunctional methacrylate ester, SR-9012 trifunctionalacrylate ester, SR-9041 pentaacrylate ester, SR-909 proprietary,SR-NTX-5249 proprietary, CD-550 methoxy polyethylene glycol (350)monomethacrylate, CD-582 alkoxylated cyclohexane dimentanol diacrylate,CD-611 alkoxylated tetrahydrofurfuryl acrylate CD-800 proprietary(Sartomer), CD-9042 proprietary (Sartomer), CD-9044 proprietary(Sartomer), CD-9051 trifunctional acid ester, CD9052 trifunctional acidester, CD-9075 proprietary (Sartomer), and CD-9088 proprietary(Sartomer). Suitable monomers may also include the following oligomermaterials available from Sartomer: CN966A80 urethane acrylate blendedwith tripropylene glycol diacetate, CN963B80 urethane acrylate blendedwith tripropylene glycol diacetate, CN985B88 proprietary (Sartomer)urethane acrylate blended with ethoxylated (3) trimethylopropane,CN963E75 triacrylate urethane acrylate blended with ethoxylated (3)trimethylopropane, CN982E75 , urethane acrylate blended with ethoxylatedtrimethylolpropane diacrylate, CN966R60 urethane acrylate blended withethoxylated (4) nonyl phenol acrylate, CN981B88 urethane acrylateblended with 1,6-hexanediol diacrylate, and CN966J75 urethane acrylateblended with isobornyl acrylate, CN-975 hexafunctional urethaneacrylate, and CN-968 urethane acrylate.

It will be appreciated that different monomers, oligomers, and/ormixtures thereof may be better suited for different printing systems,printing applications and/or printing mediums. For example, as describedabove, printheads designed for use with aqueous-based printing fluidsmay require a printing fluid to have a relatively low viscosity forproper printhead performance. Therefore, embodiments configured for usewith such printheads may utilize low-viscosity monomers (for example,with a viscosity of approximately 15 cps or lower) as a majoritycomponent of the printing fluid, with smaller combinations of higherviscosity and/or higher functionality monomers as appropriate. Specificexamples of monomers that may be suitable for such printing fluidsinclude those listed in the following table, available from Sartomer andfrom the Cognis Corp., USA of Cincinnati, Ohio.

Part Number Chemical Description Viscosity Sartomer SR484 Octydecylacrylate 4 SR395 Isodecyl acrylate 5 SR440 Isooctyl acrylate 5 SR2562-(2-ethoxyethoxy) ethyl acrylate 6 SR285 tetrahydrofurfuryl acrylate 6SR335 Laurel acrylate 6 SR489D Tridecyl acrylate 7 SR506 IsobornylAcrylate 8 SR212B 1,3-butylene glycol diacrylate 9 SR238 1,6 hexanedioldiacrylate 9 SR508IJ dipropylene glycol diacrylate 10 SR247 Neopentylglycol diacrylate 10 CD611 alkoxylated tetrahydrofurfuryl acrylate 11SR339 2-Phenoxyethyl acrylate 12 SR531 Cyclic trimethylolpropane formalacrylate 13 SR9003IJ Propoxylated neopentyl glycol diacrylate 15 CognisPHOTOMER Propoxylated neopentyl glycol monomethyl 8 8127 etherdiacrylate PHOTOMER Tripropylene glycol monomethyl 8 8061 ether acrylatePHOTOMER Myristyl acrylate 8.5 4814 PHOTOMER 1,6-Hexanediol diacrylate 94017 PHOTOMER dipropylene glycol diacrylate 10 4226 PHOTOMER Hexadecylacrylate 10 4816 PHOTOMER Decanediol diacrylate 12 4102 PHOTOMERTripropylene glycol diacrylate 15 4061

A printing fluid according to the present disclosure may include themonomer or mixture of monomers in any suitable amount. Examples ofsuitable amounts include, but are not limited to, amounts betweenapproximately 20 weight percent to approximately 99 weight percent. Insome embodiments, monomer concentrations between approximately 50 and 90weight percent may be used. In general, the greater amount of monomerused, the greater the solids content in the printing fluid. Where amixture of monomer is used, the individual components may have anysuitable concentrations within these ranges. For example, where aprinting fluid contains a mixture of a low-viscosity mono-functionalmonomer and a di-functional or higher functional monomer, thedi-functional or higher functional monomer may be present in aconcentration of approximately 5-20 weight percent, and themono-functional monomer may comprise a majority (i.e. 50% by weight ormore) of the printing fluid. Such a mixture may provide a fluid having asuitably low viscosity for thermal ejection and may form a suitablydurable cured film.

In some embodiments, the monomer mixture may have the right volatilitycharacteristics to be vaporizable by the firing resistor and form asufficiently strong bubble to act as its own driver fluid. In otherembodiments, the monomers and/or monomer mixtures may not besufficiently volatile. In these embodiments, an additional volatiledriver fluid may be used to drive the ejection of the fluid uponheating. Any suitable driver fluid may be used as an additional driverfluid. Suitable additional driver fluids include fluids that are atleast partially miscible with the monomer or monomer mixture to avoidseparation from the monomer, fluids that have a sufficiently low boilingpoint and/or energy of vaporization to form a sufficiently large bubblefor proper printing performance, and/or fluids that require little or nodrying after curing (for example, fluids that may be included in asufficiently small amount to be incorporated into the cured polymermatrix, that evaporate when exposed to the curing energy source, and/orthat otherwise do not interfere substantially with the curing of thefilm). Examples of suitable additional driver fluids include, but arenot limited to, fluids having a boiling point below approximately 75degrees Celsius, such as acetone, methyl or ethyl acetate, low alcoholssuch as methanol, ethanol and propanols, and mixtures thereof.

The use of such an additional driver fluid may allow a non-aqueous orsubstantially non-aqueous printing fluid to be used with manycurrently-manufactured thermal ejection printheads designed for aqueousprinting fluids while avoiding a slow-drying aqueous formulation withpotentially poor solubility in the monomer or monomer mixture.Furthermore, the use of acetone or a lower alcohol or acetate as adriver fluid may allow the driver fluid to be more easily removed fromthe printed film than an aqueous-based solvent due to the lower polarityand higher volatility of the lower alcohols, acetates and acetonecompared to water. As used herein, the term “nonaqueous” may refer tocompositions in which a small amount of water may be present, forexample, due to its presence in the alcohol prior to formulation, and/ordue to atmospheric water, but to which water was not added as anintended ingredient. Likewise, the term “substantially non-aqueous” mayrefer to solutions in which water is present in a relatively lowconcentration (for example, less than 10 weight percent), but to whichthe water is added as an intended or incidental component (for example,via an aqueous pigment dispersion or emulsion, etc.). Such printingfluids may offer the advantage over aqueous (as well as some otherhigh-solvent printing fluids) that the printed fluid does not need to bedried with a heat source before curing. However, it will be appreciatedthat some water may be added to embodiments of the disclosed printingfluids, depending upon the intended use for the fluids.

The driver fluid may be included in a printing fluid according to thepresent disclosure in any suitable concentration. Suitableconcentrations include, but are not limited to, concentrations from 0(with the use of a suitable monomer as a driver fluid) to 50 percent byweight. In more specific embodiments, the driver fluid may be present ina range of between approximately 15 and 35 percent by weight.

Under some conditions and with some printing fluids, the repeated firingof the firing resistor can result in the buildup of residue, sometimesreferred to as “koga”, on the resistor surface. This process may bereferred to as “kogation.” Kogation may be considered a “charring” ofprinting fluid components on the firing resistor surfaces. Kogation mayresult in a loss of drop velocity and drop weight of the individualprinting fluid droplets ejected. Without wishing to be bound by theory,the koga may either disrupt the even growth of the bubble by providinglow energy nucleation sites, or may interfere with heat transfer byacting as a thermal insulator. The loss of drop weight over the lifetimeof the printhead may reduce the optical density of the printing fluid onthe paper, and may also reduce the accuracy of droplet placement,thereby degrading print performance.

It has been found that, in the absence of preventative measures, thermalprintheads may suffer relatively short lifetimes when used to printcurable printing fluids due to kogation. Therefore, to increase thelifetime of the printheads, a resistor protectant configured to preventkogation may be included in the printing fluid.

Without wishing to be bound by theory, some resistor protectants mayfunction as surfactants that bind to the resistor surface and preventother printing fluid components from undergoing reactions on theresistor surface. Firing resistors are often coated with an outersurface layer of a refractory metal material, such as titanium,zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,tungsten, gold or silver, to help reduce cavitation damage to theresistor caused by the collapse of the drive bubble after fluid dropletejection occurs. Resistor protectants in the printing fluid may bind tothe metal, and hydrocarbon and/or alkoxy functional groups on theresistor protectants may help to prevent the adsorption of dyes and/orother printing fluid components onto the metal resistor coating. Theseresistor protectants thereby may help to prevent surface reactions thatmay degrade the adsorbed ink components into insoluble deposits.

In some embodiments, the resistor protector may be included as part ofanother component. For example, some commercially available colorantsolutions may include surfactants or other compounds with resistorprotectant ability. In other embodiments, a resistor protectant may beadded as a separate printing fluid component. In these embodiments, anysuitable protectant may be used. Examples of suitable resistorprotectants include, but are not limited to, phosphate esters with astructure of (R—O-E_(x))_(y)PO_((4-y))H_((3- y)), wherein R is abranched hydrocarbon, unbranched hydrocarbon, or perfluorinatedhydrocarbon moiety with at least eight carbons, E is an ethoxy group(—CH₂CH₂O—) or a methyl ethoxy group (—C(CH₃)HCH₂O—), X is 0 or apositive integer, and Y is an integer from 1 to 3. More specificexamples of suitable resistor protectants include compounds from thechemical class tridecyl alcohol ethoxylates. Specific examples ofcommercially available suitable resistor protectants that may help toincrease printhead lifetime include DEXTROL OC-70 (phosphate ester oftridecyl alcohol ethoxylate), DEXTROL OC-22 (phosphate ester of nonylphenol ethoxylate), STRODEX MO-100 (phosphated alcohol) and STRODEXP-100 (phosphate coester of alcohol and aliphatic ethoxylate) fromDexter Chemical of New York, N.Y.; STEPFAC 8171 (nonylphenol POE 6phosphate ester), STEPFAC 8180 (phosphate esters of an alkylpolyethoxyethanol), STEPFAC 8181 (phosphate ester of an alkylpolyethoxyethanol), and STEPFAC 8170 (nonylphenol POE phosphate ester)from the Stepan Company of Northfield, Ill.; MAPHOS M-60A (aliphaticphosphate ester), and MAPHOS 8135 (aromatic phosphate ester) from BASFof Ludwigshafen, Germany; and ULTRASIL PE-100 (dimethicone PEG-8phosphate) from ULTRASIL Corporation of Haywood, Calif.

These resistor protectants may be effective in protecting resistors withmany common types of outer resistor surface materials, including but notlimited to resistors with titanium, zirconium, hafnium, vanadium,niobium, tantalum, chromium, molybdenum, tungsten, gold, silver andplatinum outer layers.

The resistor protectant may be present in a printing fluid according tothe present disclosure in any suitable concentration. Suitableconcentrations include, but are not limited to, concentrations betweenapproximately 0.1-10 weight percent. In more specific embodiments, theresistor protectant may be added to the printing fluid in aconcentration of approximately 2-6 weight percent or volume percent.

A printing fluid according to the present invention may be configured tobe cured via any suitable energy source. For example, in someembodiments, the printing fluid may be configured to be cured byexposure to an electron beam after printing. In these embodiments, theelectrons in the electron beam have sufficient energy to initiate thepolymerization of the curable monomer components of the printing fluid.Such a printing fluid may also be cured by exposure to an ion plasma.The printing fluid may be configured to be curable by exposure to anelectron beam (or other particle radiation) or ion plasma having anintensity of approximately 50 to 500 mJoules/cm², or may be configuredto be curable by exposure to an electron beam (or other particleradiation) or ion plasma having either a higher or lower intensity.

In other embodiments, the printing fluid may be configured to be curableby exposure to ultraviolet radiation. In these embodiments, the printingfluid may include a photoinitiator that creates free radicals upon theabsorption of UV light. The free radicals then initiate thepolymerization of the curable monomer or monomer mixture. UV light ofany suitable wavelength and energy intensity may be used to cure theprinting fluid. For example, the printing fluid may be configured to becurable by exposure to UV light having an intensity of approximately 50to 500 mJoules/cm², and/or by exposure to UV light having a wavelengthof between 220 and 450 nm.

Any suitable photoinitiator or photoinitiators may be used in a printingfluid according to the present disclosure. Examples include, but are notlimited to, benzophenone, trimethylbenzophenone, methylbenzophenone,2-hyroxy-2-methyl-1-phenyl-1-propanone, benzyl dimethyl ketal, isopropylthiooxanthone, 1-hydroxy-cyclohexyl-phenyl-ketone, ethyl4-(dimethylamino) benzoate, and like compounds. Examples of suitablecommercially available initiators include IRGACURE 369(2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone),IRGACURE 907(2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one), IRGACURE1300 (30% 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone and 70% 2,2-dimethoxy-1,2-diphenylethan-1-one),DAROCUR ITX (mixture of 2-isopropylthioxanthone and4-isopropylthioxanthone), IRGACURE 819 (phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide), IRGACURE 500 (mixture ofbenzophenone & 1-hydroxycyclohexyl phenyl ketone), and IRGACURE 379(2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one)from Ciba Specialty Chemicals of Tarrytown, N.Y.; CN386 (amine acrylate& acrylic ester) from Sartomer of Exton, Pa., and ESACURE KTO46 (amixture of trimethylbenzoyldiphenylphosphine oxide, a-hydroxyketones,benzophenone derivatives) and ESACURE TZT (a mixture of 2,4,6trimethylbenzophenone & 4 methylbenzophenone) from Lamberti SPA ofItaly. Furthermore, in some embodiments, more than one photoinitiatormay be used. For example, in some embodiments, different photoititiators(and/or coinitiators) may be used to cure the surface and the bulk ofthe printed fluid. Examples of suitable coinitiators include, but arenot limited to, N-371 reactive amine coinitiator CN-386 reactive aminecoinitiator, CN-372 reactive amine coinitiator, CN-384 reactive aminecoinitiator, CN-383 reactive amine coinitiator, and CN-373 reactiveamine coinitiator, all from Sartomer.

The photoinitiator may be present in a printing fluid in any suitableconcentration. Examples of suitable concentrations of photoinitiatorinclude, but are not limited to, concentrations in the range of betweenapproximately 0.1-20 weight percent.

In some embodiments, the printing fluid may be configured to have nocolor and/or to print a clear film onto a printing medium. Such aprinting fluid may be used, for example, as a build fluid to whichcolorants may be added, or as a protective coating or adhesion layer. Inother embodiments, the printing fluid may include one or more colorants.Suitable colorants include, but are not limited to, pigments, dyes,pigment-resin systems, and combinations thereof.

A colorant may be added to a printing fluid according to the presentinvention in any suitable amount. Suitable amounts of colorant ormixtures of colorant include amounts that give a desired colorintensity, brightness, hue and/or saturation, and/or amounts thatprovide a desired chemical or physical characteristic (for example,surface tension, viscosity, boiling point, etc.) to the printing fluid.Examples of suitable amounts of colorant include, but are not limitedto, colorants in a concentration of 0.1-20 weight percent.

As mentioned above, in some embodiments, one or more oligomers may beadded to the printing fluid. Oligomers may be used to adjust variousphysical properties of the cured printed film, including chemicalresistance, flexibility, weatherability, and shrinkage. Suitableoligomers that may be added to a printing fluid according to the presentdisclosure include but are not limited to acrylated urethanes, epoxies,polyesters and acrylics. Furthermore, the oligomers may be added to theprinting fluid in any suitable amounts. Suitable amounts include, butare not limited to, amounts in a range of approximately 0.1 to 80percent by weight.

Various other additives may also be added to a printing fluid accordingto the present disclosure. For example, an adhesion promoter may beadded to the printing fluid composition, wherein the adhesion promotermay be configured to bind the cured printed film more strongly to theprinting medium. Any suitable adhesion promoter may be used. Examples ofsuitable adhesion promoters include compounds within the chemical classof 1, 2 butyl glycol diacrylate ester. It will be appreciated that thechoice of adhesion promoter may depend upon the properties of the mediaon which the printing fluid will be used.

It will further be appreciated that adhesion promoters, oligomers andcolorants are merely examples of types of additives that may be used inconjunction with a printing fluid according to the present disclosure,and that other suitable additives may also be used. Other types ofadditives that may be added include surfactants, defoamers, levelers,co-solvents, compatabilizers, dispersants, antiblocking additives, andadditives for scrub resistance, matting, water repellency, anti slip,increased gloss, Theological properties, viscosity depressants, andincreased transparency.

EXAMPLES

To measure the effect of selected resistor protectants on the lifetimeof a thermal fluid ejection printhead, a control UV-curable printingfluid was prepared with 30% by volume, and a series of experimentalblack-pigmented UV-curable printing fluids containing 30% methanol byvolume were prepared, each having 3% by volume of a resistor protectant.The total number of drops fired per resistor before failure is shown inthe right-hand column of the below table. An asterisk in the right-handcolumn indicates that the printhead was still good after the number ofdrops shown had been fired.

Resistor Protectant Millions of drops fired Control with no additive0.45 DEXTROL OC-70 8.60* DEXTROL OC-22 5.50* STEPFAC 8171 3.43* STEPFAC8180 3.25 STRODEX MO-100 3.14* STEPFAC 8181 2.56 MAPHOS M-60A 1.54STRODEX P-100 1.33 MAPHOS 8135 1.15 STEPFAC 8170 1.15 ULTRASIL PE-1000.78 CHEMPHOS 444 0.55 MAPHOS M-60 0.49 CHEMPHOS 421 0.45

A control UV-curable printing fluid was also prepared with 30% ethanolby volume, and a series of experimental black-pigmented UV-curableprinting fluids containing 30% ethanol by volume were prepared. Thetotal number of drops fired per resistor before failure is shown in theright-hand column of the below table, and the concentration of resistorprotectant is shown in the center column. An asterisk in the right-handcolumn indicates that the printhead was still good after the number ofdrops shown had been fired.

Resistor Protectant Protectant (% volume) Millions of Drops FiredControl with no 0 0.45 additive DEXTROL OC-70 3 >2.7*

Black-pigmented UV-curable printing fluids having 3% by volume ofDEXTROL OC-70 as a resistor protectant were also prepared with otherdriver fluid compositions than pure methanol and pure ethanol. The totalnumber of drops fired per resistor before failure is shown in theright-hand column of the below table, and the driver fluid compositionis shown in the center column. An asterisk in the right-hand columnindicates that the printhead was still good after the number of dropsshown had been fired.

Resistor Protectant Driver Fluid (% volume) Millions of Drops FiredDEXTROL OC-70 10% MeOH + 10% 8.60* EtOH DEXTROL OC-70 30% isopropylalcohol >2.92* DEXTROL OC-70 10% MeOH + 10% >2.25* EtOH + 10% Acetone

Various different compositions of printing fluids according to thepresent disclosure have been prepared and successfully printed and curedvia a thermal fluid ejection printhead and UV lamp, respectively.Several exemplary compositions are as follows:

Exemplary Composition 1 Component Weight % of Printing Fluid SR508IJ49.65 CN386 6.67 SR1135 5.34 SR1137 4 BYK-088 (anti-foaming additive)0.33 IRGASTAB UV-10** 0.17 DEXTROL OC-70 3.3 Black Dispersion 9B-898*6.67 Methanol 23.7 BYK-3500 0.17 *available from Penn Color ofDoylestown, PA **available from Ciba Specialty Chemicals

Exemplary Composition 2 Component Weight % of Printing Fluid SR440 22.92SR212 28.51 CIBA 907 5.50 CIBA 1300 5.50 CIBA ITX 1.10 Black Dispersion9B-732 (Penn Color) 9.77 DEXTROL OC-70 3.00 Methanol 23.70

Exemplary Composition 3 Component Weight % of Printing Fluid SR508 25.36SR212 28.51 CIBA 907 5.50 CIBA 1300 5.50 CIBA ITX 1.10 Black Dispersion9B-732 7.33 DEXTROL OC-70 3.00 Methanol 23.70

Exemplary Composition 4 Component Weight % of Printing Fluid SR508 51.43CIBA 907 5.50 CIBA 1300 5.50 CIBA ITX 1.10 Black Dispersion D3110K* 9.77DEXTROL OC-70 3.00 Methanol 23.70 *available from RJA Dispersions ofMapelwood, MN

Exemplary Composition 5 Component Weight % of Printing Fluid SR506 25.36SR212 28.51 CIBA 907 5.50 CIBA 379 1.65 CIBA ITX 1.10 CIBA 651 3.85Black Dispersion 9B-898 (Penn Color) 7.33 DEXTROL OC-70 3.00 Methanol23.70

Exemplary Composition 6 Component Weight % of Printing Fluid SR506 40.32Black Dispersion 9B-898 (Penn Color) 7.33 CN131B 7.33 BYK-088 0.37BYK-3500 0.37 CN386 7.33 SR1135 5.86 SR1137 4.40 DEXTROL OC-70 3.00Methanol 23.70

Exemplary Composition 7 (Yellow Fluid) Component Weight % of PrintingFluid SR440 23.82 SR212 28.59 CIBA 907 5.50 CIBA 1300 5.50 CIBA ITX 1.10Blk Disp 9Y-686 8.80 DEXTROL OC-70 3.00 Methanol 23.70

Exemplary Composition 8 (Magenta Fluid) Component Weight % of PrintingFluid SR440 25.66 SR212 28.59 CIBA 907 9.90 CIBA ITX 1.10 BlackDispersion 9R-715 8.06 DEXTROL OC-70 3.00 Methanol 23.70

The printing fluids disclosed herein may be used in a wide range ofapplications and may be configured to print on a wide range of mediathan is possible with conventional aqueous thermally ejectable printingfluids. Examples of potential media and applications include, but arenot limited to, mail printing and package marking and coding on mediasuch as glossy non-porous surfaces such as plastics, glass, metal,offset printed material as well as on green (wet) wood, porous ceramicand paper products. Many such media may cause conventional thermallyejectable printing fluids to bleed down the fibers causing fuzzy print,or coalesce or bead, thereby creating a poor quality print with a sloweddrying time and increased risk of smearing. However, a printing fluidaccording to the present disclosure may permit high-definition prints tobe made that dry almost instantly and fix in place with substantially nobleed or color mixing. Such prints may be able to be handled immediatelywithout smearing or marring, and may be waterfast upon curing.

Printing of a printing fluid according to the present disclosure may beperformed in any suitable manner. One example of a suitable method ofprinting with the disclosed printing fluids is as follows. First, theprinting fluid may be provided to a thermal fluid ejection printhead.Next, current is directed through one or more firing resistors in thefluid ejection printhead, thereby causing the vaporization of the driverfluid, which forms a bubble and causes the ejection of one or moredroplets of printing fluid from the printhead onto a printing media.After the printing fluid has been transferred to the printing media, thefluid on the printing media may be exposed to an energy source to causepolymerization of the printing fluid, which may occur rapidly.

The printing media and printhead may be moved relative to one another inany suitable manner to effect printing. For example, in someembodiments, the printing media is moved adjacent to the printhead in abatchwise manner, while in other embodiments, the printing media ismoved adjacent to the printhead in a continuous manner. In yet otherembodiments, the printhead may be moved relative to a stationary mediaor a moving media. Likewise, the curing also may be performed in anysuitable manner. For example, the printing media may be exposed toultraviolet light or other electromagnetic radiation to initiate curing.Alternatively, the printing media may be exposed to an electron beam, aplasma, or other source of particle radiation.

Although the present disclosure includes specific embodiments, specificembodiments are not to be considered in a limiting sense, becausenumerous variations are possible. The foregoing embodiments areillustrative, and no single feature, component, or action is essentialto all possible combinations that may be claimed in this or laterapplications. The subject matter of the present disclosure includes allnovel and nonobvious combinations and subcombinations of the variouselements, features, functions, and/or properties disclosed herein. Thefollowing claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “a” or “a first” element or the equivalent thereof. Such claimsshould be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Further, ordinal numbers, such as first, second, and third, foridentified elements or actions are used to distinguish between theelements and actions, and do not indicate a required or limited numberof such elements or actions, nor a particular position or order of suchelements or actions unless otherwise specifically stated. Othercombinations and subcombinations of features, functions, elements,and/or properties may be claimed through amendment of the present claimsor through presentation of new claims in this or a related application.Such claims, whether broader, narrower, equal, or different in scope tothe original claims, also are regarded as included within the subjectmatter of the present disclosure.

1. A curable printing fluid composition for a thermal fluid ejectiondevice, comprising: a curable liquid-phase monomer; a substantiallynonaqueous volatile driver fluid capable of being vaporized by a thermalfluid ejection printhead; an initiator; a phosphate ester resistorprotectant; and a colorant comprising a dispersed pigment.
 2. Thecomposition of claim 1, wherein the liquid-phase monomer comprises anacrylic monomer.
 3. The composition of claim 2, wherein the liquid-phasemonomer further comprises a mixture of two or more acrylic monomers,wherein at least one of the acrylic monomers is a monofunctional monomerand wherein at least one other of the acrylic monomers is a difunctionalmonomer.
 4. The composition of claim 1, wherein the monomer is thedriver fluid.
 5. The composition of claim 1, wherein the driver fluidcomprises at least one of methanol, ethanol, acetone, methyl acetate andethyl acetate.
 6. The composition of claim 5, wherein the compositioncomprises approximately 50% or less driver fluid by total compositionvolume.
 7. The composition of claim 5, wherein the composition comprisesapproximately 15-35% driver fluid by total composition volume.
 8. Thecomposition of claim 1, wherein the phosphate ester resistor protectanthas a general formula of (R—O-E_(x))_(y)PO_((4-y))H_((3-y)), wherein Ris a branched hydrocarbon, unbranched hydrocarbon, or perfluorinatedhydrocarbon moiety with at least eight carbons, E is CH₂CH_(x)O orC(CH₃)HCH₂O, x is zero or an integer greater than zero, and y is aninteger from 1 to
 3. 9. The composition of claim 1, wherein thecomposition comprises approximately 1-6% resistor protectant compound bytotal composition volume.
 10. The composition of claim 1, furthercomprising an oligomer.
 11. The composition of claim 10, wherein theoligomer is selected from epoxies, polyesters, acrylics, and acrylicurethanes.
 12. The composition of claim 10, wherein the compositioncomprises approximately 0.1-80 weight percent of oligomer by totalcomposition weight.
 13. The composition of claim 1, wherein thecomposition is UV-curable and wherein the initiator comprises aphotoinitiator.
 14. The composition of claim 13, wherein thephotoinitiator comprises at least one of benzophenone,trimethylbenzophenone, methylbenzophenone,2-hydroxy-2-methyl-1-phenyl-1-propanone, benzyl dimethyl ketal,isopropyl thiooxanthone, 1-hydroxy-cyclohexyl-phenyl-ketone, ethyl4-(dimethylamino)benzoate,2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one,2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone,2,2-dimethoxy-1,2-diphenylethan-1-one, phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide,2-dimethylamino-2-(4-methyl-benzy)-1-(4-morpholin-4-yl-pheny)-butan-1-one),amine acrylate, acrylic ester, trimethylbenzoyldiphenylphosphine oxide,a-hydroxyketones, and benzophenone derivatives).
 15. The composition ofclaim 1, wherein the composition comprises 0.1-20 percent photoinitiatorby total composition weight.
 16. The composition of claim 1, furthercomprising an adhesion promoter.
 17. The composition of claim 16,wherein the adhesion promoter comprises a 1,2 butyl glycol diacrylicester.
 18. The composition of claim 16, wherein the compositioncomprises 0.1 to 20 percent adhesion promoter by total compositionweight.
 19. The composition of claim 1, wherein the composition has aviscosity of less than or equal to approximately 20 cps under conditionsof use in a thermal fluid ejection device.
 20. The composition of claim1, wherein the monomer has a viscosity of approximately equal to or lessthan 15 cps under conditions of use in a thermal fluid ejection device.21. The composition of claim 1, wherein the composition has a surfacetension of between approximately 20-50 dyne/cm.
 22. A thermal inkjetprinting cartridge comprising a printhead and a UV-curable printingfluid composition for a thermal fluid ejection device, the printingfluid composition comprising: at least one di-functional acrylicmonomer; at least one substantially nonaqueous driver fluid present inan amount of 0.1-50 weight percent by total composition weight; at leastone photoinitiator and at least one amine present in a combined amountof 0.1-18 weight percent by total composition weight; a dispersedpigment; and at least one phosphate ester resistor protectant present inan amount of 0.1-10 weight percent by total composition weight.
 23. Thecartridge of claim 22, wherein the composition has a viscosity equal toor less than approximately 20 cps.
 24. The cartridge of claim 22,wherein the composition has a surface tension of between approximately20-50 dyne/cm.
 25. The cartridge of claim 22, further comprising amono-functional acrylic monomer present in an amount of 0.1-90 weightpercent by total composition weight.
 26. The cartridge of claim 22,wherein the di-functional acrylic monomer is present in an amount of0.1-90 weight percent by total composition weight.
 27. The cartridge ofclaim 22, wherein the substantially nonaqueous driver fluid comprises atleast one of a lower alcohol, a lower acetate, and acetone.
 28. Thecartridge of claim 22, wherein the substantially nonaqueous driver fluidis present in an amount of 5-40 weight percent by total compositionweight.
 29. The cartridge of claim 22, wherein the photoinitiator ispresent in an amount of 5-20 weight percent by total composition weight.30. The cartridge of claim 22, wherein the phosphate ester resistorprotectant has a general formula of (R—O-E_(x))_(y)PO_((4-y))H_((3-y)),wherein R is a branched hydrocarbon, unbranched hydrocarbon, orperfluorinated hydrocarbon moiety with at least eight carbons, E isCH₂CH_(x)O or C(CH₃)HCH₂O, x is zero or an integer greater than zero,and y is an integer from 1 to
 3. 31. The cartridge of claim 22, whereinthe resistor protectant is present in an amount of 2-6 weight percent bytotal composition weight.
 32. The cartridge of claim 22, wherein thecomposition further comprises a colorant.
 33. A curable,thermally-ejectable printing fluid composition, comprising: at least oneliquid-phase monomer; at least one substantially nonaqueous driver fluidvaporizable by a thermal fluid ejection printhead; one or morephotoinitiators; one or more amine coinitiators, wherein the one or morephotoinitiators and the one or more amine coinitiators are included inthe printing fluid at a concentration of 12-18 parts per totalcomposition weight; a pigment dispersion stabilized by the one or moreamine coinitiators; and at least one phosphate ester resistorprotectant, wherein the composition is curable by exposure to at leastone of electromagnetic energy and particle energy, and wherein thecomposition has a viscosity of approximately 1-20 cps under conditionsof use in a thermal fluid ejection device and a surface tension ofapproximately 20-50 dyne/cm.
 34. The composition of claim 33, whereinthe at least one monomer comprises an acrylic monomer.
 35. Thecomposition of claim 34, wherein the acrylic monomer comprises amono-functional acrylic monomer and a di-functional acrylic monomer. 36.The composition of claim 33, wherein the at least one driver fluidcomprises at least one of methanol, ethanol, a propanol, a butanol,acetone, methyl acetate, and ethyl acetate.
 37. The composition of claim33, wherein the at least one phosphate ester resistor protectant has ageneral formula of (R—O-E_(x))_(y)PO_((4-y))H_((3-y)), wherein R is abranched hydrocarbon, unbranched hydrocarbon, or perfluorinatedhydrocarbon moiety with at least eight carbons, E is CH₂CH_(x)O orC(CH₃)HCH₂O, x is zero or an integer greater than zero, and y is aninteger from 1 to
 3. 38. The composition of claim 33, further comprisinga colorant.
 39. The composition of claim 33, wherein the coinitiator ispresent in an amount of 4 percent by total composition weight.
 40. Thecomposition of claim 33, further comprising an adhesion promoter.